Device for testing the center of gravity of rapidly rotating parts of machinery



@Amm i5 192451.,

DEVICE F'da H. HORT f TESTING THE CENTER OF- GRAVITYOF RAPIDLY ROTATING PARTS OF MACHINERY Filed May'lS. 1922 3 shams-sheet x AWE I5 1924.

1,490,109 H. HORT DEVICE FCR TESTING THE CENTER 0F GRAVITY 0E RAPIDLY ROTATING PARTS 0F MACHINERY Filed May l5. 1922 3 Sheets-Sheet 2 E ne* P2 WWW@ \ lll/143429,.

pm 15, 1924. n,49o,109

. H. HORT DEVICE FOR TESTING THE CENTER 0F GRAVITY OF RAPIDLY ROTATING PARTS 0F MACHINERY Filed May 15 1922 3 Sheets-Sheet 5 Patented Apr. l5, 1.924.

n was HERMANN HORT, F ESSEN, GERMANY, lASSIGNOR TO FRIED. KRUP'P AKTIENGESELL- 1SCHAFT, OF ESSEN-ON-@HE-RUHR, GERIWANY.

DEVICE FOR TESTING THE CENTER OF .GRAVITY OF RAPIDLY ROTATIG 0F MACHINERY.

Application led May 1 5, 1922. Serial No. 561,237.

To all whom t mag/ concer/n.'

Be it known that I, l-IERMANN HORT, residing at Essen, Germany, a citizen of the German Republic, have invented a certain new and useful Improvement in Devices for Testing the Center of Gravity of Rapidly Rotating Parts of Machinery, of which .the following is a specification.

This invention relates to devices for dy- J namically determining t-he position of the center of gravity lof rapidly rotating parts of machinery.

The static method employed for this purpose and having for its object. to put the center of gravity of the machinery part into its axis of rotation, offers no security that the machinery part will rotate quietly, that means, that it will not transfer onto its supports, because of its rotation, forces which have a transversedirection with respect to the axis of rotation of the part to be tested.

Forces ofthis kind cannot arise only in the Lcase the axis of rotation of the machinery part coincides with one of the main axes of 256 its ellipsoid of inertia. Therefore, the devices for dynamically determining the position of thel center of gravity have for their object to determine the position of one of the vmain axes of the said ellipsoid of inertia 3Q with respect to the axis of rotation of the machinery part to be tested and to enable, in

this way, to put thisA main axis onto the said axis of-rotation.

The invention has for its special object to produce a device -of the character stated which enables to determine thet position of the ellipsoid of inertia with a comparatively small number of revolutions of the machinery part, in contradistinetion to known devices of this kind which permit of this testing operation to be carried out, only with a.

generally Very. high, and therefore critical,`

,number of revolutions.

The object aimed at is realized by the arrangement, construction and combination of parts to be hereinafter described and particularly pointed out in the; appended claims.

Cn the annexed drawings five embodiments of the subject-matter of the invent-ion are illustrated by way of example,

Figl showing an axial longitudinal Section of the first embodiment,

Fig. 2 an elevation of Fig. l, seen from the left,

Fig. 3 a in elevation,

Fig. 4 a view, corresponding to Fig. 1, of a portion of the third embodiment,

Fig. 5 a view, corresponding-to Fig. l, of the fourth embodiment,

Fig. 6 a section on line 6 6 of Fig. 5, seen from the left,

Fig. 7 a. section on line 7-7 of Fig. 5 seen from above,

Fig. 8 a front view of the fifth embodiment,

Fig. 9 a section on line 9 9 of Fig. 8, seen from the left, and

Fig. 10 a section on line 10-10 of Fig. 8, seen from above.

rl"he embodiment shown in Figs. l and 2 will be described first, this embodiment being designed for dynamically testing machinery parts which have to be supported by meansof freely extending separate pivots.

portion of the second embodiment.

Referring now to the drawings, A is the stationary frame of the device in which a stirrup-shaped frame vB having two vertically extending legs B1 and B2, is mounted for rotation by means of a vertical hollow pivot '53. The legs B1 and B2 support two bearing pans b4 and b5 on which a bent-down carrier C is mounted for oscillation by means of knife-edges c1 and c2.

Cn'the carrier C there is mounted for rotation a conical pivot D the object of which is to receive the machinery part E to be tested. Theaxis of this pivot D lies in the middle plane, of the carrier C, passing through the bearing edges of the knives c1 and 02 and is at right angles to the axis of the knifeedge b4 c1. b5. c2. On the carrier C are further provided twolvrpointers c3 situated oppo site-cach other and having indicating edges which lie in the above-mentioued middle plane of the carrier C and are in parallel with the axis of the pivot D. Furthermore, two pointers c* (Fig: 2) are mounted on the carrier C opposite each other and having indicating edges whiclnlikewise are in parallel with the axis of the pivot D and lie in a plane passing through the axis of this pivot and running at right angles to the abovementioned middle plane of the carrier C. The frame B carries a pointer bf which faces a graduation plate c5. This plate is connected t the carrier C and shows a circular graduation.

Finally, two centering screws c11 and c1 (Fig. l) are provided on the carrier C, 0pposite to plates 67 and which are fixed to the legs B1 and B2, these centering screws being intended to prevent the carrier C from moving in the direction of the axis of the knife-edge bearing b1 c1, b5, c2. The carrier C along with the parts permanently connected to it (D, c?, 'c4 c5 etc.) is balanced 7for itself so that one of the main axes of its ellipsoid of inertia exactly coincides with the axis of rotation of the pivot D. On the leg B1 of the frame there is further fixed an llshaped frame b9 one of the two parallel legs of which carries a setscrew F serving to adjust a pointer f1. This latter faces a graduation b1 and can be shifted with respect to the frame b9. On the set-screw F is fixed one end of a tension spring G (Fig. 2) the other end of which is attached to the carrier C. A. second tension spring G1 is interposed between the frame b1 and the carrier C, the pulling force of which spring acts against that of the spring G.

In the'hollow ivot b3 of the frame B is lodged a shaft so as to rotate and undergo longitudinal displacement. On its free end facing the carrier C this shaft has a conical recess h1 which, inthe position of the parts shown in Figs. l and 2, is engaged by a centering point d1lof the pivot D. The shaft H is under the action of a spring J tending to shift it towards the carrier C and abutting against a collar provided on a hollow sha-ft K. This latter is lodged likewise in the hollow pivot 3, coaxially withthe shaft H, and capable of rotating but not of being'shifted. The shaft H passes through the hollow shaft K and is connected thereto by a slot and key connection so as to be capable of beingl shifted with but not of rotating with, the shaft K.

On its lower end the shaft H has fixed on it a disk h2 which foi-ms the abutment for one arm, L, of an angle-lever .mounted for oscillation on the'stationary frame A f the device. The other arm, L1, of the angle- A lever L L1 can be fixed on a toothed arc .1

rigidly connected of a latch.

The shaft K is surrounded by a hollow shakt K1, these two shafts beingintercon` nected by slot and key so as to be shifted but not to rotate relatively to eachother. The shaft K1 possesses a helical lgroove permanently engaged by a pin Z211 fixed on the hollow pivot b3. At its lower end the shaft K1 carries a loose ring M non-displaceably mounted on it and having two pins m1 and m2 engaging respective slots of an arm N of an angle-lever pivoted on the frame A. The other arm,\N1, of the angle-lever N N1 can be fixed ,on a toothed' arc a1 connected to the frame'A, by ineansyof a latch n2 (Fig.

to the frame A, by means Finally the hollow pivot b3 carries a ifieaioe bevel wheel 612 which is in mesh with a handoperated bevel wheel a3 mounted on the frame A (Fig. 2)'.

Before the testing opeiation the parts take the relative position shown in Figs. l and 2. The springs G and G1 are so adjusted, by means of the set-screw F that they will maintain the carrier C in a position in which its middle plane passing through `the bearing edges of the knives c1 and 02, passes through the axis of the hollow pivot 3, this latter axis thus coinciding with the axis of the pivot D. The angle-lever L L1 is being fixed in a position so that the shaft H assumes the likewise fixed so that the shaft K1 is prevented from being shifted and, therefore, is coupled with the hollow pivot b1`by means of the pin Z211.

Before dynamically determining the center of gravity of the machinery part in question, the latter has to be tested statically that means, its center of gravity must be brought to lie inthe axis of rotation of the part. The partE is then' placed upon the pivot Dv and the frame Bset in rotation by means of the bevel gear a3 512. This rotation is taken part in by the carrier C and is transferred also onto' the shafts K1, K and H, since the hollow pivot b3 is coupled to the shaft K1 and this latter, through the intermediary of the shaft K, to the shaft H.

As soon as the frame B has reached a certain angular velocity which is, however,

comparatively small, the arm L1 of the anglelever L L1 has to be rocked in the direction of arrows (Fig. l) until ykthe recess h1 of the shaft H, displaceable by means of the angle-lever L L1, has almostfully released the centering point d1 of the pivot D so that this point will project into said recess to a small cxtentvonly. Thereupon the lever .arm L1 Ais fixed again on the toothed arc a1 Now the carrier C is able to swing out, about the axis of its knife-edge bearing, with i'evspect to the frame B which continues to rotate, until the centering point d1 will touch the surface of the conical recess h1.

As the axis of rotation of the machinery part generally will not precisely coincide Inf) with one of the main axes of the ellipsoid of f inertia of the part, a couple of forces will arise, according to known rules of dynamics, during the common rotationof the frame B and the part to be tested, which couple of forces will lie-in a plane passing through the will cause a rotation of the latter about its knife-edge bearing. Owing to the rapidl increasing reaction of one of the springs or .G1 this rotation, however/will remain, Awithin the range determined by the touching of the point d1. on the surface of the recess L1, limited to a comparatively. small amountf The size of the angle of rotation `about the axis of the pivot D up to such an angular position lthat the plane ofthe couple of forces will pass through the axis of the knife-edge bearing of the carrier C. In this case the turning moment of the couple of forces with respect to the axis of the knifeedge bearing is equal to zero so that the pointer beno longer will indicate a deflec- -tion. In order to realize the above-men tioned problem the recess h1 of` the shaft I-I .r is brought, while-the frame Ycontinues to rotate, into'v full engagement`with the centering point d1 by returning the angle-lever L L1 into its 4initial position. Further the lever arm N1, after releasing the latch n2, is turned a certain amount opposite to the direction of arrow This rotation of the angle-lever N N1 causes the shaft K1 to move towards the frame B, the pin b11'of the hollow pivot b3 engaging the helical groove 7a2 of the shaft K1 compelling thisshaft to turn with respect` to the hollow pivot b3 which turning -movement is transferred, through the intermediary. of the shaft K coupled for,rotation both to the shaft K1 and I-I, to this latter shaft I-I and from it through the friction clutch h1 d1, on to the pivot D alongv with the part E to be tested, thus causing this latterto undergo a rotary displacement relatively to its carrier C. Now the clutch d1 `L1 is disengaged again thus causing the carrier C to swing out with respect to the further rotating frame B by an angle-which generallycan be read off again on the pointer 6G., The machinery part is thenfonce more turned with respect to the carrier C in the described manner and this turning isrepeated until the carrier C will no longer show a defiect-ion. As soon-as this is the case. the plane of the couple of forces will pass through theiaxis of the knife-edge b4 c1, b c2 and. consequent-ly.`one of the main axes of the ellipsoid of inertia of the part E lies in a yplane passing through the axis of the .pivot Dand that ofthe knife-edge bearingv b4 c1, b5 c2. This plane intersects the shell surfaceof the part E along lines which.

will come .to be marked on the part E through the intermediary of the pointers c3.

after the device has been brought to a stand- Sau.

Now the part'E has to'be turned by 90.o with respect to the 'carrier C by means of the gearing-'N1 N, M, K1, K H h1 d1 D sothat 7" the lines marked thereon will be exactly opsite the indicating edges of the pointers c* Fig. 2). `Then the device is started again. With the angular position the part E now assumes with respect to the carrier C, the

couple of forces acting on the part E upon rotation is of the same size as the turning moment exerted by it with respect to the axis of the knife-edge bearing b1 c1, b5 c2 on the carrier C, as the plane of said couple offs() forces is at right angles to the axis of said bearing. If, therefore, the tension of the springs G and G1 is altered by means of thei set-screw F until the pointer be will no longer indicate a. defiection of the carrier C S5 upon rotation of the frame.y B and with the clutch disengaged, the turning moment exerted upon the carrier C by the springs G and G1 will exactly be equal to the turning moment of said couple of forces. LThe9 amount of said turning moment is read off on thegraduation 51. Thus the amount of the couple of forces is known and, since the plane in which this couple of forces is acting is already known` the position of the main axis in question of the ellipsoid of inertia of the part to be tested can be determined without difficulty by calculation and can be, 1n a known mamier, so corrected by conveniently altering the distribution of. 10

the masses that the main axis of inertia will coincide with the axis of rotation. f

In the case of the second embodiment illustrated in Fig. 3 the moment 'of the couple of forces is not balanced by adjustable tension springs but by the centrifugal force of adjustable weights. To this end the carrier C ,has fixed on it at both sides of its middle plane,. two parallelarms c* and 09 each a shifting weight O and O1. In other respects the arrangement k,of the parts is the same as in the first described embodiment.

Upon testing the machinery part E the two weights have to bevshifted always by the same amount butin yopposite directions until ythe carrier C will no longer deflect. The sizeand distance away of t-he weights O and O1 will give a measure for the amount carrying of the moment of the couple of forces. In

`ject the carrier C of the device is accom-i illustrated in Fig. 4' is designed for dynamically balancing parts of machiner f having two journals. In accordance with this obplished by a bridge portion C10 so as to form a closed two-part frame C C10 within which the part E to be tested can-be mounted for rotation bymeans of its journals e1 and e2. Detachably connected to the journal e1 is a sleeve P having a. centering point p1 like the former point d1 and adapted to ngage the recess k1 of the sha-ft H. In other respects the device entirely corresponds to the first described embodiments as regards both construction and manner of operation.

The fourth embodiment shown in Figs. 5 to 7 is likewise designed fory test-ing machinery parts hai-*ing two journals. In this case the frame B is mountedfor rotation in the stationary frame A of the device byv means of twohollow/pivots b3 and b1t. A sleeve K1 mounted on the hollow pivot b3 so as to be shifted thereon but not to rotate in dependently and corresponding to the shiftable shaft K1, carries a pin avhich engages in a helical groove fs provided on a shaft ist.

'This shaft K4 corresponds to the forme-r sha-ft K and is rotatably lodged in the hollow pivot baybut cannot be shifted thereon. By means of an angle-lever N N1 the sleeve K1 can be shifted in the same ma'nner as the .former shaft K1. The shaft K1 carries a bearing pan le upon which rests the knife g1 of a bearing body Q. Cn its end'remote from the knife g1 the body Q is provided with a bearing pan g2 forming the abutment for a knife-1)3 of a sleeve P2 which corresponds to the sleeve P of Fig. 4, the arrangement being such that the bearing edge' of the knife p3 is at right angles to the knife g1. The two knife-bearings It g1 and Q2 p3 thus form a. Cardan joint.

The sleeve P2 is'detachably connected to one, e1, of the journals of the machinery part E to'be tested while its other journal e2 is rotatably held in a. sleeve It. engaging, by means of a thorn-shaped extension lr1 (Figs. 6 and 7), in a bearing pant, This pan Z915 is pro- .vided on a bridge b1 integral .with the frame` B. The extension r1 is held in engagement with the pan 615 by twosprings S and S1 one of the l ends of which is fixed to the bridge 510 while Yso their otherI ends are attached to projections r? and r3 of the sleeve R. In the same manner as y the carrier C of the former embodiments the sleeve R is subjected to the action of two coiled springs G and G1 the common axis of which is at right angles to that of the extension r1 of the sleeveR (Fig. 7) The springs are in connection with indicating devices not shown in the drawings. Finally the sleeve R has a recess r1 into which may enter a centering pointlrt of a shaft h3, the latter corresppnding to the former shaft. H and being s ftable in the hollow pivot 614 by means of the angle lever L L1. l. The remaining parts embodiment. v

rEhe device works in the following manner:

The couple of forces acting on the ma chinery part E upon rotation and the plane of which passes through the axis of rotation of the part E and through a main axis lof its ellipsoid of inertia is brought, by rotarily displacing the part E with respect to the frame B by means of the gearing N1 N, K1 176:", '5 K4 if, g1 Q g1, v3 P1, into a posit-ion such as to cause its plane to pass through the point of the thorn-shaped extension r1 of the sleeve It and, consequently, be at right angles to t-he common axis of the springs Gand G1. AWhen in this position, the couple of forces .will notexertany effec-t upon the springs Gr and G1, and this can be stated by the indicating devices (not shown) connected to these springs. Thereupon the part E is turned by 90", relatively to the frame B, out of the position just ascertained. In this new position the couple of forces exerts its greatest effect' upon the springs G and G1 from the tension of which, as indicated by the indicating devices, the amount of said couple of forces and, further, the wanted position of the main axis of inertia can be found by calcu# lation. i

In the fifth embodiment of the invention shown in Figs. 8 to l() the frame B is mount.- ed to'rotate about a. horizontal axis. carrier C is mounted for oscillation in the frame B by means of two coaxial centering points 01,1 and 012. The machine-ry part to be tested is rotatably mounted on'the carrier C by means of its journals e1 and e1 and takes suoli a position relative-ly to the carrier C that its center of gravity l lies in the axis of the two centering points 011 01.2.

Asin the embodiment of Fig. 4 a slee-ve I), having a centering point p1, is detachably yconnected to one, e1, of thefjournals o'f the part E. This centering point 211 forms one half of a releasable friction clutch, the other half is formed lby acollar, having a recess h1, of a shaft I-I, as in the embodiment of Fig. 4. rI'lie other journal, '62, of the part E carries a sleeve R5, corresponding to the sleeve R of Fig. 5 and to which one end of two coiled springs and G1 is attached. The other end of these springs is connecte-d each toa set-screw F 2. and F3 respectively. The set-screws F2 Ft` are ixedin the parallel legs of a I l-shaped -frame b17 which is fixed on the frame B and corresponds to the frame b9 of Figs. l and 2. The conditions are such as to cause the common axis of the set-screws F2 and F? to be at right angles to that of the centering points 011 and "012.

The plane of the couple offorces-acting upon the machinery part E is brought, in this case also, at first into a position in which The.

it coincides withthe middle plane of thc cari rier C determined by t-he common axis of the centering points c and cl2 and the axis of rot-ation ot' the part E. Thereafter the part E is displaced by 90 relatively. to the carrier C and with this new position ot the part. E, the lnoment of the couple of forces is measured.

Claims:

l. A device for dynamically determining the. positionof the center of gravity of a body. comprising a rot-ating frame. a sta rotating said body` about'its central axis relative tosaid' frame.

Q.. A device for dynamically determining` the position ot the. center of gravity of a body. comprising a 4rotating frame. a stationary support for said frame. a swinging bearing supported on said ltrame and rotating therewith, said body being supported by said swinging 'bearing and having its centra-l axis in the line with the axis of rotation of said frame`v means for independently rotating said' bddy about its central axis relative to saidframe. andmeans for indieating the position-.of the plane containing one of the `main axes of the ellipsoid of inertia of the body and the central axis of the body.

3. A. device'for dynamically determining the position ot the center of gravity of a body.- 'comprising a rotating frame. a stationary support Afor saidframe. a swinging bearing supported on said frame and rotating therewithasaid body being supported by said swinging bearing-and having it-s cen-v tral axis in the line with' the axis' of rotation of said frame. means for independently rotating said body about its vcentral axis rela.- tive to said frame. means for indicating the position of the plane containing one of the main axes of the elllipsoid offine'rtiaof the body and the central axis of the `body. and means yfor maintaining said swinging bear- ,in-g in'its normalposition against the disturbing force occurring when. said last named axes do not coincide,

4. A' device for dynamic-ally determining the position of the center of gravity ofa body. comprising a rotating frame. a stationary support for said frame, a bridge pivotally supported at two opposite .points in said :trame'and rotating therewith,y said body being supported on said bridge and having its central axis in the line'with the axis of rotation of Said frame and means for independently rotating said body about its central axis relative to said frame.

5. A. device for dynamically determining theposition of the center of gravity of a body, comprising a. rotating'frame. a sta tionary support for said frame, a bridge pivotally supported at two opposite points in said frame and rotating therewith, said body being supported on said bridge and 'having its central axis in the line with the axis of rotation of Said frame. meansV for independently rotating said body about its central axis relative to said frame and means for indicating the position of the plane containing one of the main axes of theellipsoid of inertia of the body and the central axis oi" tbe body.

6. A device for dynamically determining the position of the center of gravity of a body. comprising a rot-ating frame.a stationary support for said frame. abridge pivotallysupported at two opposite points in said frame and rotating therewith, said body being supported on said bridge and having its central axis in the line with the axis of rotation of said frame. means for `independently rotating said body about its l central axis relative to said frame. means for indicating the posit-ion of the plane containingone of the main axes of the ellipsoid ot inertia of the body and the central axis of the body` and means for maintaining said bridge in its normal position against the disturbing forceoccurring when said last named axes do not coincide.

7. A, device for dynamically determining the position of the center of gravity of a body. comprising a rotating vertical frame, a stationary supportfor said frame, a horizontal bridge -pivotally supported at two opposite points in saidframe and rotating therewith. a vertical mountingfmember for said body revolubly supported on Said bridge. said mount-ing member having its central axis normally in the line with the axis ot rotation of said frame, and means `for holding said alignmentjor allowing a 'limited swinging movement of said bridge relative tosaid frame.

8. A device for dynamically determining the position of the center of gravity of a body comprising a.. rotating vertical frame. a stationary support for said frame, a horizontal bridge pivotally supported at two opposite points finsaid frame and rotating therewith, a vertical mounting member for said `body revolubly supported on said bridge. said Vmounting member having its central axis normally in the line with the axis of rotation of said frame, means for holding said alignn'ient or allowing a limited swinging. movement of said bridge relative to said frame. said means comprising a vertical shaft inA said frame and having its axis coincident therewith, an axially dise 'posed detent in t-he top of said shaft, an axially disposed downward projection of inverted-cone shape on said mounting member,

f and `means for causing said projection to en- A zontal bridge pivotally supported at two opter said detent to a predetermined extent.

9. A device for dynamically determining the position of t-lie center of gravity of a` body, comprising a rotat-in vertical frame, a .stationaiysupport for said frame, a horiposite points in'said frame and rotating therewith,y a vertical mounting member for said body revolubly supported on said bridge, said mounting member having its central axis normally in the line with the axis of rotation of said frame, a vertical shaft in said frame and having its axis coincident therewith, an axially disposed detent in the top of said shaft, an axially disposed downward projection of inverted-cone shape on said mounting member, said shaft longit-udinally displaceable for causing the engagement of said project-ion in said detent.

10. A device for dynamically determining the position of the center ofgravit-y of a body, comprising a rotating vertical frame, a stationary support for said frame, a hori` zontal bridge pivotally supported at two op- .posite points in said frame and rotating therewith, a vertical mounting member for said body revolubly supported on saidl bridge, said mounting member having its centralaxis normally in the line with t-lie axis of rotation of said frame, -a vertical shaft in said frame and having its axis co incident therewith, a friction clutch between said mounting member and said vertical shaft, means for engaging said clutch, and means for rota-ting said vertical shaft relative to said frame. y

11. A device for dynamically determining the position of the center of gravity of a body, comprising a rotating vertical frame, a stationary support for said frame, a horizontal bridge pivotally supported Jat two opposite points in said frame and rotating therewith, a vertical mounting member for ,said body revolubly supported on said bridge, said mounting member having .its central axis normally in the line with the axisof .rotation of said frame, a vertical shaft rotatably and displaceably mounted needle@ hollow shaft surrounding said first-named shaft, a high pitch screw connection between said hollow shaft and said frame, said firstnamed shaft being displaceably but nonrotatably mounted in said hollow shaft and means for displacing said hollow shaft for the purpose of rotating said first-named shaft relative to said frame.

12. A device for dynamically determining i movement of said bridge relative to said frame.

` '13. A device for dynamically determining the position ofthe center of gravity of a body, comprising a rotating vertical frame, a stationary support for said frame, a horizontal Vbridge pivotally supported at two opposite points in said frame and rotating therewith, 'said body being mounted onl said bridge, opposite-acting elastic tension members attached to said bridge distant from its horizontal axis and to said frame for controlling the swinging movement of said bridge relative to said frame, and means for adjusting said tension members in compensation to the swinging force of ysaid bridge.

14. A device. for dynamically determining the position of the center of gravity of a body, compi'isiiig a rotating vertical frame, a stationary support for said frame, a horizontal bridge pivotally supported at two opposite points in said frame and rotating therewith, said body being mounted on said bridge, opposite-acting elastic tension meintrolling the swinging movement of 1said bridge relative to said frame, means for ad- .justing said tension members in compensation to the swinging force of said bridge,

and a scale cooperating with said adjusting means for measuring said swinging force.

The foregoing specific-ation signed at Essen, Germany, this 12th day of April, 1922. HERMANN HORT. 

